The exemplary embodiment relates to diketopyrrolopyrrole (DPP)-derivatives, such as small molecules, oligomers, and semiconducting polymers based thereon and in particular to polymers comprising a DPP moiety connected to two five-membered heteroaryl rings at the 3 and 6 positions of the DPP moiety. These polymers find application in semiconductor layers of electronic devices such as organic thin film transistors (OTFTs). However, the exemplary embodiment is not limited to such applications.
Semiconducting layers are found in many electronic devices, including thin film transistors (TFTs), and sensors, image scanners, and electronic display devices comprising them. OTFTs offer advantages over conventional, silicon-based materials in that manufacturing costs can be reduced as well as providing mechanical properties such as the devices being physically compact, lightweight, and flexible. OTFTs are generally composed of a supporting substrate, three electrically conductive electrodes (gate, source and drain electrodes), a channel semiconductor layer, and an electrically insulating gate dielectric layer separating the gate electrode from the source and drain electrodes. The channel semiconductor is in turn in contact with the source and drain electrodes. The materials used to make the OTFTs, and the interfacial properties between various layers of semiconductor, dielectric, and electrodes can all affect the performance of the OTFTs.
Thiophene-based fused-ring small molecules and polymers are high mobility p-type semiconductors which have been used for thin film transistors. However, due to the relatively high HOMO (highest occupied molecular orbital) energy level of these materials, most of them are sensitive to oxygen and therefore not suitable for fabrication of devices under ambient conditions.
For example, thieno[3,2-b]thiophene-based polymers have shown high field effect mobility of 0.2-0.6 cm2/Vs (See, e.g., McCulloch, I., et al. Nat. Mater. 5, 328 (2006)). However these polymers have shown some sensitivity towards oxygen and moisture in air, thus hampering their solution fabrication of TFTs in ambient conditions.